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Doc Nickel
05-16-2011, 08:31 PM
This weekend's latest tool score was a 40-ton Christensen hydraulic press:

http://www.docsmachine.com/fabshop/40T-1.jpg

Price was a reasonable $150, but as is the case for most of my purchases, it needs work. The seller said there's something wrong with the pump, possibly even parts missing. I haven't opened it to look. It's a side-mounted reservoir with two handles- apparently one is high-volume to move the ram quickly, the other is low volume for power.

http://www.docsmachine.com/fabshop/40T-2.jpg

Any chance someone has a diagram or manual for this pump? Possible source of parts? Exploded view?

Doc.

wierdscience
05-16-2011, 08:46 PM
Take it back,the pump is missing the dipstick:D

Oh Ya,you suck too:D
$150,you powerful suck:D

Now that we have that out of the way,those pumps are dirt simple,should have just check balls and some o-rings inside,McMaster should have all the rubber you'll need.

Doc Nickel
05-16-2011, 11:31 PM
Take it back,the pump is missing the dipstick:D

-That tube on the near corner in the photo isn't for a dipstick, it's for an unpressurized return line from the ram. (Probably just a drip tube for seal weepage.)

And yeah, this was kind of a stealth tool-gloat post. Nyah! :D

Currently trying to dismantle the pump. Not having much luck- I think an O-ring is jammed in a snap-ring groove...

Doc.

Doc Nickel
05-17-2011, 04:53 AM
Okay, I finally have most of the pump module disassembled. An interesting unit, made largely of fabricated pieces welded together, and then enclosed in a thick steel tank.

The seller, as I noted above, seemed to think there were actually parts missing from the pump. That's probably true, since the high-volume pump cylinder only contained these parts:

The ram and it's threaded cap...
http://www.docsmachine.com/fabshop/40T-3.jpg

... a check ball...
http://www.docsmachine.com/fabshop/40T-4.jpg

... and this ring/spacer with a crosspin.
http://www.docsmachine.com/fabshop/40T-5.jpg

I suspect the check ball was supposed to go under the spacer, and seat on the opening at the bottom of the pump's tube.

But there's no seal or wiper or O-ring on the ram, and no packing or seal of any kind- nor a groove or step to accept one- in the threaded cap. As I was dismantling it (still with oil in the reservoir) it'd leak oil profusely as the ram was raised.

I'm assuming there's some sort of seal I'm missing, and possibly some part (a cup?) on the ram, but I have no idea what they are or what they look like. Anyone have any suggestions or sources?

Doc.

wierdscience
05-17-2011, 08:51 AM
Ya.looks like the piston is missing,easy enough,just machine one up from Aluminum and machine a groove for one of these "O-ring loaded lip seals"-

http://www.mcmaster.com/#mechanical-seals/=ccd5c3

If the threaded collar has no seals,which it wouldn't need anyway,I would cut a groove for and install a wiper seal like the "shaft wipers" just to keep dirt out.

A new ball bearing for the checks,I usually get two,one of which I weld to the end of a 1/4" rod and use for a lapping tool to polish the rust off the seat.

Oh,and there should be two checks on the HV cylinder,one inlet ball and one spring loaded outlet check.

lazlo
05-17-2011, 10:12 AM
Wow, what a score! Looks like the stiffeners are 1/2" plate -- don't make them like that anymore!

You've assembled quite the professional machine shop Doc -- it's come a lone way since your 9x20 :)

Alistair Hosie
05-17-2011, 01:42 PM
I love how you guys buy things take them apart and make a real repair, or work out what's wrong. I find this stuff really interesting keep up the good work and great press wish |I had room for one although I would probably never use it in reality.Alistair

Doc Nickel
05-17-2011, 03:13 PM
Ya.looks like the piston is missing,easy enough,just machine one up from Aluminum and machine a groove for one of these "O-ring loaded lip seals"[.]

-I'm assuming the piston would go above the existing steel disc? And that it'll tighten against the taper to seal the inner bore of the piston?


If the threaded collar has no seals,which it wouldn't need anyway,I would cut a groove for and install a wiper seal like the "shaft wipers" just to keep dirt out.

-So there shouldn't be any oil above the piston?


Oh,and there should be two checks on the HV cylinder,one inlet ball and one spring loaded outlet check.

-There's check balls everywhere. I got at least five out of this thing. There's two checks between the handles, one below the handwheel, and one at the bottom of each pump. I was planning on replacing all of them, as several have rust, but that's a good idea on the lapping of the seats.

Doc.

Doc Nickel
05-17-2011, 03:17 PM
Wow, what a score! Looks like the stiffeners are 1/2" plate -- don't make them like that anymore!

-Actually, they're closer to 5/8", and the uprights are 3/4".

And they must not make 'em like this anymore- I can find exactly one small photo online of another Christensen, a 25T on a machine sales site. No info on the company, no info on the presses, no one else seems to have mentioned their press in passing on a board somewhere...

The date on this thing is something like 9-68, and was sold by Star Machinery Company out of Seattle/Spokane. But apart from knowing that, it appears to be an old orphan brand now...

Doc.

macona
05-17-2011, 03:29 PM
Or you can do what I did, replace the hand pump with a port-a-power pump. Electric, that is.

Doc Nickel
05-17-2011, 05:23 PM
The seller said that what he'd intended to do, but before he could, he got a good deal on a 50-ton Dake.

It's always possible, of course, but I'd prefer the manual pump for the time being. (That and I'd rather not blow $300+ on an electric power pack at the moment. :D )

Doc.

wierdscience
05-17-2011, 08:42 PM
-I'm assuming the piston would go above the existing steel disc? And that it'll tighten against the taper to seal the inner bore of the piston?

Yes,that's what I am seeing.


--So there shouldn't be any oil above the piston?
If there isn't a seal in that cap,then there couldn't be,it would leak every stroke.



--There's check balls everywhere. I got at least five out of this thing. There's two checks between the handles, one below the handwheel, and one at the bottom of each pump. I was planning on replacing all of them, as several have rust, but that's a good idea on the lapping of the seats.

Doc.

The two in the pump bottoms should be inlet checks,gravity operated,the two between the handles will be outlet checks and spring loaded?And the one under the handwheel will be the return block.

The two inlets and the return block will be the most important.

Did you get into the cylinder yet?

wierdscience
05-17-2011, 08:45 PM
The seller said that what he'd intended to do, but before he could, he got a good deal on a 50-ton Dake.

It's always possible, of course, but I'd prefer the manual pump for the time being. (That and I'd rather not blow $300+ on an electric power pack at the moment. :D )

Doc.

With as big as that HV pump is,it will prbably out pace the porta power pump anyway.

Doc Nickel
05-17-2011, 11:01 PM
One other bit: On the pump ram, there's a snap ring toward the lower end, just above the tapered portion.

http://www.docsmachine.com/fabshop/40T-3.jpg

This snap ring, and it's mating groove, show signs of abuse- as if the ram had been raised to the max upward stroke, regularly and forcefully. The clip is bent slightly concave, and the groove's edge is peened slightly.

However, the underside of the threaded cap shows no damage or wear at all. If the damage on the shaft came from being raised rapidly and forcefully, it must have hit something besides the cap.

What that other thing could have been is beyond me, though.

An alternate theory is that the damage came when someone tried to remove the now-missing piston. The nuts, threads and disc at the end, however, show no damage, so... ?

Doc.

wierdscience
05-17-2011, 11:48 PM
You got me,that setup is a bit unusual.

Lu47Dan
05-17-2011, 11:52 PM
Doc, could the snap ring be the upper travel limit of the pump? I have had a couple of piston hand pumps apart and they either had a heavy snap ring or a reduced upper shaft diameter with a sharp shoulder as the stop.
How tight is the fit between the piston and the cylinders wall? If the pistons edges were polished and then the cylinder honed to a very close tolerance fit a HV low pressure pump would pump oil at low pressures.
Dan

Doc Nickel
05-18-2011, 06:15 PM
Doc, could the snap ring be the upper travel limit of the pump?

-It does, and that's what I'd assumed the ring was there for. My question is, that it's sustained damage from excessive force, and from the direction as if someone had, in fact, been slamming it against the upper threaded cap repeatedly and forcefully, but there is no trace of matching damage on the cap itself. No wear, no peening, no marks, nothing.

That makes me think there was something between the cap and the snap ring, though I can't think what that might have been.


How tight is the fit between the piston and the cylinders wall? If the pistons edges were polished and then the cylinder honed to a very close tolerance fit a HV low pressure pump would pump oil at low pressures.

-It's pretty close, and I have no doubt it'd pump oil with reasonable efficiency. But without a seal on the piston and no seal on the upper cap, there's nothing to keep fluid from building up above the piston, and then being pumped overboard through the cap. There has to be a seal in there somewhere.

Doc.

Doc Nickel
05-18-2011, 06:26 PM
Next question: The two check balls between the pump cylinders and the output to the ram are held in place with threaded plugs with a long "pin" on the end. The pin I'm presuming limits the travel of the check ball, and the plug is a straight thread with a copper washer for a seal.

One of the two plugs has been damaged- it looks like somebody may have dropped an extra check ball in place, or one considerably oversized, and tried to tighten the plug back in place.

This distorted the threads slightly, and actually bent the pin (which is just mild steel.)

I was going to make a new plug, but it's an oddball thread: approximately 19 tpi, and .517" OD. It's neither a standard US thread nor a metric- at least according to my metric thread pitch gages.

What is it? Whitworth? British Straight Pipe?

Doc.

RussZHC
05-18-2011, 08:28 PM
Looks to be British Standard Pipe

http://www.oldengine.org/members/diesel/Tables/bsp1.htm

:) ?, on the linked chart 1/4" and 3/8" are 19 tpi with the 1/4" being .518

Boostinjdm
05-19-2011, 02:43 AM
I think I'd consider making a new piston with opposing seals. Then ditch the snap ring for a spacer and rubber washer or some type of spring. That way the stop has a little give. Something like a valve spring comes to mind as an option.

Lu47Dan
05-19-2011, 07:39 AM
Doc, I think you do need to make a new piston for the pump, just remember to allow for the added thickness of it.
For the plug for the check valve, If the threads are not damaged past the point of use, then why not just add a new stop rod to the plug. If I read the post correctly it has a copper compression seal on it, correct? Replacing the rod would save you from cutting the Whitworth(?) threads.
Dan.

Jaakko Fagerlund
05-19-2011, 10:45 AM
BSP G or R 1/4" plugs are readily available from the plumbing section of local hardware store, unless you guys across the sea use something of your own.

Doc Nickel
05-19-2011, 03:53 PM
Russ- Yep, looks like it is BSP. Thanks for the link.
Boost-That's my current plan, at least for the moment. The bore is 1.571", which is closer to 40mm than most of the fractional-size seals that McMaster shows (thanks Weird) so I'm trying to find a workable seal before I make the piston.

I'll probably leave the clip there, so the piston won't be taking the strain- the threads on the end of the ram are only a bit bigger than 1/4-20. The spring's a good idea though...

Question though- what do you mean by "opposing" seals? I was given to understand a lip seal worked best when there's the greatest pressure differential between the two sides of the lip.

Dan- that's what I'll probably do at this point, but as I said, whoever tried to mash it in place also slightly distorted the threads of the plug. I'd have preferred to replace it if I could, but it looks like that'll likely be more trouble than it's worth.

Doc.

Boostinjdm
05-19-2011, 09:29 PM
Russ-
Question though- what do you mean by "opposing" seals? I was given to understand a lip seal worked best when there's the greatest pressure differential between the two sides of the lip.

Doc.

Two seals like a two way hydraulic cylinder. One seal may be fine, but I would be worried about raising the handle too fast and sucking some air past the single seal. One above it facing the opposite direction would take care of that.